High current gain semiconductor device



Jan. 19,1954 B. N. SLADE HIGH CURRENT GAIN SEMICONDUCTOR DEVICE FiledApril 2]., 1950 2 sheets Sheet 1 n a T75 Pl/ASED PI/L-SED ATTORNEY Jan.

' Filed April 21, 1950 19, 1954 B. N. SLADE HIGH CURRENT GAINSEMICONDUCTOR DEVICE 2 Sheets-Sheet 2 g )7 I Pulse-0W w 0 z 4 [1567?006Ma a a/Miran M ,6

INVENTOR Bernazd/VJZdde ATTORNEY Patented Jan. 19, 1954 HIGH CURRENTGAIN DEVICE SEMICONDUCTOR Bernard N. Slade, Morristown, N. J., assignorto Radio Corporation of America, a corporation of Delaware ApplicationApril 21, 1950, Serial No. 157,246

18 Claims. (Cl. 317-235) This invention relates generally tosemi-conductor devices, and particularly relates to a semiconductoramplifier, oscillator or the like having improved electricalcharacteristics and to a method of preparing such a device.

A semi-conductor device suitable as an amplifier or oscillator comprisesa semi-conducting body and a base electrode, an emitter electrode and acollector electrode in contact with the body. The base electrode isusually a large-area electrode and is in low-resistance, non-rectifyingcontact with the semi-conducting body which may, for xample, be agermanium crystal. The emitter and collector electrodes are usuallysmallarea electrodes which are in rectifying, highresistance contactwith the crystal. For operation as an amplifier, for example, a voltageis impressed between collector andbase electrodes in the reversedirection while a voltage in th forward direction is impressed betweenthe emitter and base electrodes. Assuming an N type crystal, a negativepotential is required on the collector with respect to the baseelectrode and a positive. potential on the emitter with respect to thebase electrode. If a P type crystal is used. the potentials must bereversed. Devices of the above character are usually known astransistors.

It ha previously been assumed as evidenced by the. published literaturethat the distance between emitter and collector electrodes is criticaland should be approximately two mils or even less. This was due toexperimental evidence incheating that the gain decreases as the distancebetween. the rectifying electrodes increases. Thus, the current gain ofthe device decreases in accordance with, an exponential law sov that itis rapidly reduced to less than unity as the distance is increased. Thesmall spacing between emitter and. collector electrodes causes undesiredinteraction between the input and output circuits. Thus, when the.device is used as an amplifier','the amplifierbecomes unstable andfrequently develops a distorted output signal. This instability of thedevice is due to internal feedback which is believed to be caused by alarge value of the equivalent base resistance. The equivalent baseresistance may be defined as the partial differential; quotient of theemitter voltage with respect to the collector current while the emittercurrent is maintained constant. This equivalent base resistance may beas high as several hundred ohms. t is believed that the equivalent baseresistance preferably should be approximately 59 ohms or less to providea, semiconductor device having less internal feedback. such a device isless apt to oscillate in an amplifier circuit, causes lessdistortion'and; is generally more stable;

The current gain of the improved semi-conductor device of the inventionis considerably higher than that of previously known devices which isapproximately between 1 and 3. By increasing the current gain of thedevice the power gain may be maintained high even though the equivalentoutput resistance is decreased. The equivalent output resistance of thedevice is essentially the resistance measured when looking into thecollector electrode.

It is accordingly the principal object of the present invention toprovide an improved semiconductor device having superior electricalcharacteristics, suitable as an amplifier, oscillator or the like, andto provide an improved method of preparing such a device.

A further object of the invention is to provide a device of the typereferred to, having a lower equivalent base resistance and lowerinternal feedback than previously known transistor devices, whereby thedevice of the invention may be utilized, for example, in an amplifiercircuit which will be more stable and less liable to oscil late.

Another object of the invention is to provide a semi-conductor devicehaving a higher current gain than previously known transistor devices,whereby the power gain of the device is comparable to that of prior artdevices while the equivalent output resistance is reduced to levelsheretof'ore unattainable without reduction of power gain.

A still further object of the invention is to pro-- vide asemieconductor device which combines a desired high frequency responsewith a high current gain, a high power gain and low internal feedback.

In accordance with the present invention, a semi-conductor device iselectrically treated by impressing an electrical charge betweencollector and base electrodes in the reverse direction while a steadycurrent is permitted to flow between the emitter, collector and baseelectrodes. This electrical treatment may be called pulsing, and may beefiected by discharging a, previously charged capacitor betweencollector and base electrodes. Further, in accordance with the presentinvention, the pulsing takes place while the emitter and collectorelectrode are relatively widely spaced and no less than 10 mils andpreferably approximately 15 mils apart.

If the semi-conducting crystal has a high bulk resistivity which will bedefined hereinafter, such a pulsed device is now ready 130 use. It hasan equivalent base resistance of less than ohms and preferably of lessthan 50 ohms.

Alternatively, it is feasible toutilize a crystal having alow bulkresistivity. In that case,

:any other suitable electric conductor.

pulsing takes place in the manner previously described. However, afterthe pulsing has been efiected, the emitter electrode may be moved towardthe collector electrode so that their distance is no more than mils.Alternatively, pulsing may take place While an auxiliary or pulsingelectrode spaced from the collector electrode by not less than mils, isconnected in the circuit. After the pulsing has been finished, theauxiliary electrode is disconnected and an emitter electrode is utilizedwhich is spaced from the collector electrode by no more than 5 mils.

The novel features that are considered characteristic of this inventionare set forth with particularity in the appended claims. The inventionitself, however, both as to its organization and method of operation, aswell as additional objects and advantages thereof, will best beunderstood 'from the following description when read in connection withthe accompanying drawings, in which:

Figure 1 is an elevational view, partly in section, of a semi-conductordevice of the type to which the invention relates;

Figure 2 is a schematic circuit diagram for a semi-conductor device ofthe type shown in Figure 1, arranged for operation in accordance withthe invention;

Figure 3 is an equivalent schematic circuit diagram of a semi-conductoramplifier in accordance with the invention, the device being represented as a T network;

Figure 4 is a schematic circuit diagram of a modified semi-conductordevice and operating system therefor embodying the invention; and

Figures 5 to 7 are graphs showing, respectively, curves of the currentgain, the power gain and the equivalent base resistance plotted withrespect to the spacing of the emitter and collector electrodes ofvarious semi-conductor devices in accordance with the present inventionand of prior art devices for purposes of comparison.

Referring now to Figure 1 there is illustrated a semi-conductor deviceof the type disclosed and claimed in a copending application to GeorgeM. Rose, Jr., Serial No. 90,702, filed April 30, 1949, entitledSemi-Conductor Amplifier Construction and assigned to the assignee ofthis application (now Patent 2,538,593, issued January 16, 1951). Thedevice of Figure 1 includes a block I 0 of semi-conducting material. Theblock I0 may, for example, consist of a crystal of boron, silicon,germanium, selenium or tellurium containing a small but sufiicientnumber of atomic impurity centers or lattice imperfections as commonlyemployed for best results in crystal rectifiers. Germanium is thepreferred material 'for the block I9 and may be prepared so as to be anelectronic N type semi-conductor as is well known. The surface of block5 9 may be polished and etched as is conventional.

The block I0 is soldered or sweated to a bar I I which may, for example,consist of brass or Bar II accordingly represents the base electrode ofthe device which is in low-resistance, non-rectifying contact with bodyI 0. Bar II may have a square cross-section or a circular cross section,as shown. A stifi wire or pin I2 of conducting material such as a heavynickel wire is soldered or otherwise secured to the bar I I to provideeleca trical contact with the block I0. Semi-conducting block I6, bar II and pin I2 forms the first sub-assembly of the complete device.

4 Rectifying electrodes I3 and I4 which represent the emitter andcollector electrodes respectively, consist each of a fine, stiff,resilient fila- .ment or wire having pointed ends I5, I6. Wires Durez.Supports I1 and I8 are preferably molded into cylinder 22. Cylinder 22is provided with a central cylindrical aperture 24 through which bar IImay be pressed. The dimensions of aperture 24 and of bar I I are suchthat the bar has a press fit with cylinder 22. Preferably, pin I2 andsupports I 7, I 8 are arranged in a common plane and extend beyond thebottom of cylinder 22 to form pins which fit a standard subminiaturetube socket.

Cylinder 22, supports II, I8 and wires I3, I4 form the secondsub-assembly of the complete device. The device preferably is enclosedby housing 25 which may have a cup-shape as shown. Housing 25 mayconsist of a plastic material or of nickel-plated cold-rolled steel.Housing 25 forms the third sub-assembly of the complete device and mayhave a press fit with cylinder 22. Housing 25 has the purpose ofprotecting the semi-conducting block I0 and its point contacts frommechanical damage and from the deleterious action of the air andchemicals contained therein.

As has been more fully explained in the Rose application above referredto, wires I3 and I4 are formed with a bend intermediate their ends whichforms an acute angle with their substantially straight end portions. Byvirtue of this construction the spacing between the pointed tips ofwires I3, I4 will remain substantially constant when bar I I is pushedupwards against the wires.

In accordance with the present invention, a semi-conductor device of thetype illustrated in Figure 1 is electrically treated under certainconditions, thereby to provide a device with improved electricalcharacteristics. The forming of the device may be carried out with thecircuit shown diagrammatically in Figure 2. The device again includesblock I0 which may consist of an N type germanium crystal provided withbase electrode II, emitter electrode I3 and collector electrode I4.Battery 21 has its positive terminal connected to base electrode I Iwhile its negative terminal is connected to collector electrode I4through resistor Re. Another battery 28 has its negative terminalconnected to base electrode -II while its positive terminal is connectedto emitter electrode I3 through resistor B1. A milliammeter indicated at30 may be included in the emitter circuit for measuring the emittercurrent. Accordingly, collector electrode I4 is biased with respect tobase electrode II in the reverse direction while emitter electrode I3 isbiased with respect to base electrode I I in the forward direction.

Capacitor 3| which may be adjustable as shown, has one terminalconnected to base electrode II. Its other terminal may be connected bysinglepole double-throw switch 32 across battery 33 which has itspositive terminal connected to base electrode II. Alternatively,capacitor SI may be connected by switch 32 between collector electrodel4 and base electrode H. v

The device of Figure 2 preferably consists of a germanium body in havinga high bulk resistivity. Furthermore, the N type impurity content ofbody it} should be low. A material having a, high bulk resistivity asreferred to hereinafter is defined by a resistivity of betweenapproximately and chin-centimeter.

For a. better understanding of the invention. reference is now made toFigure 3 which illustrates the equivalent circuit diagram of thesemiconductor amplifier. The T network enclosed. within dotted box 35.schematically represents the devices The external input andoutputresistors Hi and R0 have been shown in Figure 3 as well asbatteries 2? and. 28. Rb indicates the external base resistance. The Tnetwork consists of. a vertical branch consisting of resistor Pb and ofa horizontal branch including resistors Ta and r to the junction pointof which Tb is connected.

An impedanceless generator is also indicated in.

Figure. 3 comprising the product of Tm and 1'1, where i1 indicates acurrent flowing in thedirection shown by arrow 36.

For the following discussion it is desirable to introduce the followingsymbols. Thus, RlI==Te+Tbi 1221:1111; RlZ Tb' and R22:Tc+1b. R11 is theequivalent emitter resistance, R21 is the transfer resistance, R1215 theequivalent base resistance and R22 is the equivalent collectorresistance. Since Tb is normally small against re. R22 is approximatelyequal to: Tc.

The current gain A may be defined as follows: A=R21/Rzi. Accordingly, Ais a dimensionless number. The equivalent base resistance rt may bedefined by the partial differential quotient of the emitter voltage withrespect to the collector current while the emitter current maintainedconstant. For a further explanation of. the equivalent emitter andcollector resistances and of the transfer resistance, reference is made.to a paper by J. Bardeen and W. H. Brattain which appears on pages 239to 2.77 of the April 1949 issue of Bell, System Technical Journal andwhich is entitled- Physical Principals Involved in Transistor Action(see particularly pages 249 to 251) The power gain of a semi-conductordevice may be defined as follows: G Af RZZ/4RIYI.

Referring new again to the circuit 0i Figure 2, body Hi should consist,as previously pointed out, of. av high bulk resistivity material for thedevice disclosed in Figure 2. Furthermore, accordance with the presentinvention, the distance between emitter electrode i3 and collectorelectrode Hi should be. no. less than 10 mils for the elec tricaltreatment. Preferably, this distance should be approximately 15. mils.When the two rectifying electrodes are-thus spaced, the device is readyfor the electrical treatment. To this-end, batteries'z'l and. 28. areconnected as shown in Figure 2 so that steady currents will flow throughall three electrodes ii, i3 and M. The collector current It: will bebetween .5 and 2 ma. The emitter current Io may normally be between .2and 2 ma. before pulsing- During pulsing Ie should be adjusted. to avalue between. 2 and 4 ma. The voltage of battery 28 should. be between.1 and 2 volts. The voltage of battery it should be between 20 andvolts. The voltage of battery 33 should be approximately 180 volts. Thecapacitance of capacitor 3t sheuldbe between 051 and .2 microfarad andpreferably between 3.03 and ,IQ microfarad;

1 Electrical treatment or pulsing is now eifected by throwing switch todischarge the previously charged capacitor 3! across collectorelectrodel4 and base electrode II. It will be seen that the electricaI chargewill be applied in the reverse direction. The electrical charge which isthus applied may vary between 1.8 and 36-microcoulomb and preferablybetween 5.4 and 18 microcoulomb. After pulsing, the emitter current willhave approximately the same values as before pulsing, that is, between.2 and 2 ma., while the collector current I0 increases to between 2.5and in ma. The device, thus treated, is now ready for use and may havethe form shown in Figure 1.

The unusual electrical characteristics ofthe device of the inventiondescribed in connection with Figure 2 will now be explained. To thisend. reference is now had to Figure 5' which shows the current gain Aplottedwith respect to thespacing in mils between emitter electrode 13and 001-, lector electrode M. Curve 4a shows the current gain of adevice treated as explained in connection with Figure 2 and pulsed at aspacing between the rectifying electrodes of 16 mils as indi cated byarrow 4|. It will be seen that the current gain remains substantiallyconstant for electrodespacing between 3 and 20 mils. Dotted curve 42illustrates the current gain for the same germanium crystal. In thiscase, however, the device has been pulsed with a spacing between emitterelectrode 13' and collector electrode N of 3 mils as indicated. by arrow43. It will be observed that the current gain is considerably lower,that is, approximately 2, and falls ofil rapidly as the spacing betweenthe electrodes is increased above 12 mils. It should be noted that thecollector electrode l4 remains fixed while emitter electrode [3 is movedto obtain curves M3 and 42.

For purposes of comparison, curve is shown in Figure 5, whichillustrates the current gain as shown in Figure 5 of the paper byBardeen and Brattain, above referred to. It is stated in this paper thatthe measurements were made with formed collector points. However, it isnot clear at which electrode spacing the forming was performed. Inaccordance with curve 44, the current gain drops below unity when theelectrode spacing becomes larger than 6 mils. It will also be observedthat thecurrent gain of curve 40' is over three times as large as theinitial current gain shown by curves 42 and M.

Figure 6 illustrates various curves showing the power gain in decibels(db) with respect to the electrode spacing in mils. Curves 45, 46, 4?and 48 show the power gain for four different devices made withdifferent germanium crystals. The devices were pulsed with a spacingbetween emitterarid' collector electrodes of 16 mils as indicated byarrow 50. After pulsing, the emitter electrode-was moved to obtain thepower gain at diiierent electrode spacings. It will be noted thatthe'power gain is very high and remains almost constant until thespacing between emit'-' ter and collector electrodes exceeds lfi'mils.

Curves 5i and 5?. show the efiect of. pulsing with different electrodespacing on the power gain for the same germanium crystal. Curve 5-t'wasobtained in the manner previously ex plain'ed and pulsing was effectedwith a distance between the rectii'ying electrodes of 16 mils. CurveBiwasobtained by pulsing the same device with a spacing of.the"rectifyingv electrodes of three mils asshown by arrow 53'. Curve 5 2clear Iy shows the enormous decrease of the power gain with an increaseof the spacing between the rec-i tifying electrodes for this electricaltreatment. Since curves 5| and 52 were obtained with the same crystalall other factors which might change the shape of the curves, wereeliminated. -As explained hereinabove, the device of the invention whenpulsed as shown in connection with Figure 2 should be made of asemi-conducting material having a high bulk resistivity. Curve 5d ofFigure 6 shows the relationship between the power gain and the electrodespacing when a germanium crystal with low bulk resistivity is. pulsedwith an electrode spacing of 16 mils as shown by arrow 55. At thepresent time, no explanation can be given for this phenomena. A low bulkresistivity material as referred to hereinafter is defined as a materialhaving a resistivity of less than 10 ohm-centimeter and preferablyhaving a resistivity of between approximately 2 and -8 ohm-centimeter.

Curve 5? of Figure 7 shows the equivalent base resistance Tb withvarying electrode space ing. The device was pulsed with a spacing of therectifying electrodes of 16 mils as indicated by arrow 58.- Curve 5!shows that Tb does not decrease substantially when the spacing betweenthe rectifying electrodes is approximately 10 mils or more. Accordingly,the emitter and collector electrodes of the device described inconnection with Figure 2 should be spaced at least 10 mils apart. If thespacing increases beyond this figure, Tb remains substantially constant;T11 is substantially not affected by the operating conditions such asthe emitter and collector voltages or the emitter and collectorcurrents. It is b lieved that the value of Tb depends essentially on thebulk resistivity of the semi-conducting material. Furthermore, itdepends on the spacing between the rectifying electrodes but will remainsubstantially constant when this spacing becomes larger thanapproximately 10 mils.

The physical effect which the pulsing treatment of the semi-conductordevice produces is not known at the present time. However, it isbelieved that the comparatively large electrical charge applied betweenthe collector and base electrodes breaks down the barrier layer of thecrystal. Consequently, Tc as well as R22 is decreased. Furthermore, itis believed that the pulsing improves the collectors ability to collectholes.

In order to explain more fully the changes of the electricalcharacteristics of the semi-conductor device of the invention, referenceis now made to Tables I and II below: I

Table I R11 R21 R12 R22 scmtlrd dgictor m in in ,m A

. m ohms ohms ohms ohms Maw 0810? ured lated Average" I 400 29,100 22 1,soc s2 21.1 20.0

, Table II Pogvcggaln D. Semi-conductor 5; 5 A

devlce ohms ohms ohms ohms Maw 081cm ured latcd 440 60, 000 220 35, 0002. 2 31. 0 l9. 4 320 42, 000 80 14, 000 2. 8 22. 8 19. 3 160 30,000 3016,000 2. 1 22. 0' 20. 4 360 45, 000 60 14, 000 3. 4 28. 4 20. 5 440 60,000 180 22, 000 2. 8 27. 8 19. 9 180 44, 000 50 21, 000 2. 2 23. 8 21. 5320 44, 000 23, 000 1. 8 18. 8 1 7. 6 440 65, 000 10 10, 000 7. 0 28. 224. 2 180 40, 000 10 14, 000 2. 6 23. 2 21. 0 240 47, 000 60 14, 000 3.0 22. 0 21. 0 360 60, 000 180 30, 000 l. 9 27. 0 l8. 7 360 45, 000 6014, 000 3. 2 23. 5 19. 6

' Averaga. 331 56, 500 84 18, 900 2. 9 24. 8 20.2

Table I lists the resistances R11, R21, R12 and R22 as well as thecurrent gain A. The first column identifies the twelve different devicesfor which the values are given. The last two columns show the power gainin db as measured and as calculated. The calculated power gain wasobtained from the formula given hereinabove. The twelve devices listedin Table I have been treated as described in connection with Figure 2.Table II lists the same properties for another group of twelvesemi-conductor devices. However, the devices of Table II have beenpulsed with a spacing between the rectifying electrodes of approximatelytwo mils.

A comparison of Tables I and II will show that the average transferresistance R21 of the devices of Table I is approximately one half aslarge as that of the devices of Table II. The average equivalent baseresistance R12 and the average equivalent collector resistance R22 ofthe devices of-Table I have been reduced to less than one half theaverage values of the devices listed in Table II. On the other hand, theaverage current gain of the devices of Table I is almost twice' as largeas that of the devices of Table II. Consequently, the calculated powergains of the devices of Tables I and II are substantially the same. Itwill also be noted that the measured power g ins of the devices shown inTable II are considerably higher than their calculated power gains. Thisis due to the higher internal feedback asevidenced by the higher valuesfor R12, the equiva: lent base resistance. Thus, in spite of thedecrease of R22 of the devices listed in Table I their gain remainsconstant because the current gain squared enters the gain formula whilethe gain is directly proportional to R22.

Reference is now made to the following Table III:

Table III I I a Power gain Spac- Curin db highs: Crys- R11 in R21 1n R12in R2; in rent tween ,tal, 'ohms ohms ohms ohms gain rcctlf A Mcas-Calcu-lng elecured lated trodes Inches No 1 440 120, 000 200 45,000 2.528.8 22.0 0.002 42,000 10 4,000 10.0 27.8 28.5 .015 NO 2 520 45,000 32020. 000 2.5 24.0 17.8 .002 560 30,000 10 2,500 14.0 23.8 23.4l .015 No 3320 60,000 25,000 2.5 26.9 20.8 .002 500 42,000 10 1,000 26.0 25.2 25.3:.015

Table III gives a comparison of three difierent crystals. Each of thecrystals was measured first with narrow spacing and, narrowpulsing' ofthe rectifying electrodes and then with wide spacing .and wide pulsingof the electrodes.

Table III again shows clearly the difference between the equivalentresistances, the current gain and the power gain for differentelectrical treatment. The wide variation between the measured andcalculated power gain of the narrow spaced devices is quite noticeable.This is again proof of the large instability and of the larger internalfeedback of the narrow spaced or conventional 10 have an appreciableinternal feedback as evidenced by the higher measured power gaincompared to the calculated power gain. These devices have a bulkresistivity which is too low and they are (l-lffiCilll] to manufacture.

Another semi conductor device in accordance with the present inventionwill now be described in connection with Figure .4. This device also hashigh current gain, low internal feedback and low semi-conductor device.10

Reference is now made to the following Table s w base reslstanqeiFulthermflre, @1118 device has an excellent high frequency responseTable IV Power Stability Semi-conductor E R- E: Bl} Wave device volts Ima chins volts 3 ohms a gg form a o. 6' 1. 2 500 35 s. a 10K 22. 2"8494x122 st 25% .30 s r v 344M119 .31 .33 500 25 4.1 1 17. .65 .62 50025 3. 0 10K 19.8

In Table IV the emitter voltage Be, the emitter current It, theresistance R1 (see Figure 2), the collector voltage Ec, the collectorcurrent I0 and the resistance R0 (see Figure 2) have been shown.

Furthermore, the power gain, the stability of the device during the testand the wave form are shown. The first column identifies five difierentdevices. The first row for each device indicates the measured values ata certain date while the second row indicates the same values measuredafter a period of 66 days. It will be seen that the change of theoperating characteristics is extremely small. Also, the power gaindecreases very little. This stability over a period of 66 days isappreciably better than that of conventional semi-conductor devices. Thedevices listed in Table IV were selected and not all devices exhibit thesame stability over a long period of time.

It may also be pointed out that a device in accordance with theinvention has been used successfully in a relaxation oscillator. In atest operation, the oscillator was turned on .every mornin and turnedoff at night and no adjustments of the circuit impedances of the supplyvoltages or current were required over a test period of several weeks.The relaxation oscillator used for this test is of the type disclosedand claimed in a copending application to E. Eberhard, Serial No.70,661, filed on January 4, 1949,

and assigned to the assignee :of this application.

It will accordingly be seen that the semi-conductor device as disclosedin connection with Figure 2 has a low internal feedback and a very highcurrent gain. Because of its frequency response range, it isparticularly suitable for audio applications and for low speed counters.The current gain however is found to decrease at frequencies above 58kilocycles (kc). Three semi-conductor devices had a current gain at kc.that ranged between 2.35 and 4.25. The current gain of 17 devices at '1kc. ranged be tween 1.6 and 6.0. As will be seen in particular fromTable I the equivalent base resistance is in all cases no more than 100ohms and pref- .erably should be below ohms.

It will also be observed from Table II that some of the devices have avery low value of the equivalent base resistance R12. In spite of theirlow equivalent base resistance, however, they still which is comparableto that of conventional semiconductor devices.

The semi-conductor device of Figure l includes semi-conducting body I0.Body lil should consist of a low bulk resistivity material as definedhereinabove. The device is further provided with base electrode 1 I,emitter electrode I55, collector electrode .14, and with an auxiliary orpulsing electrode 60. In accordance with the present invention, pulsingelectrode is a rectifying electrode and may be a point electrode asshown; its distance from collector electrode 14 should be not less than10 mils and preferably approximately 15 mils. On the other hand, thedistance between collector electrode 14 and emitter electrode l3 shouldbe no more than 5 mils and preferably approximately 2 mils.

The circuit of Figure 4 shows how the device may be electricallytreated. To this end, base electrode H is grounded while collectorelectrode 14 is grounded through resistor R and battery 21. Capacitor 3|may be charged by battery 33 when switch 32 is turned to the left. Afterthe capacitor has been charged, it may be discharged between collectorelectrode 14 and base electrode H by throwing switch .32 in the otherdirection. Auxiliary electrode 60 now serves as an auxiliary emitterelectrode. It is biased by battery 61 having its negative terminalgrounded. The positive terminal of battery 6-! is connected throughresistor SZand switch 563 to auxiliary electrode .68. Switch 60 is asingle-pole double-throw switch arranged for connecting or disconnectingthe battery 6! to auxiliary electrode 58. Emitter electrode l3 may beconnected by switch 54 to re.- sistor R1 and battery 28.

The device is now treated in the manner previously disclosed. Switches83 and 64 have the positions shown in Figure 4. Hence, emitter electrodeI3 is disconnected while auxiliary electrode .60 is connected in thecircuit. After the electrical treatment is completed, switch $3 isDefined while switch E l may be closed. The dfilice now ready for .use.Auxiliary electrode oil is not connected in the circuit and may even beremoved. Emitter electrode 13 serves its normal purpose and an inputsignal may, for example, be impressed on resistor R1 While the amplifiedoutput signal may be derived from resistor R0.

The device of Figure 4 may take the form shown in Figure 1 having anadditional auxiliary electrode and an additional conducting supporttherefor similar to supports IT or [8. The device may be electricallytreated after it has been assembled. The auxiliary electrode 60 is thendisconnected, for example, by cutting off its support at the base ofcylinder 22. Alternatively, it is feasible to move auxiliary electrode60 after the pulsing has taken place. In that case, the distance betweencollector electrode l4 and auxiliary electrode 60 should be no more thanmils and emitter electrode l3 may be dispensed with because auxiliaryelectrode 60 now serves as emitter.

A semi-conductor device formed as explained in connection with Figure 4has a high current gain and a low internal feedback. Furthermore, itsequivalent base resistance is less than 70 ohms.

Its frequency response is excellent for frequencies below 1 mo.(megacycles) and it may be used at frequencies up to 3 me. However, thesemi-conducting material used for this device can not have a high bulkresistivity because in that case the equivalent base resistance would betoo high.

There have thus been disclosed improved semiconductor devices. Thedevices are formed electrically by impressing a charge between thecollector electrode and the base electrode in the reverse direction. Atthe same time, a steady current is permitted to flow between thecollector electrode, the base electrode and an emitter or auxiliaryelectrode while the distance between the collector electrode and theemitter or auxiliary electrode is no less than mils. The result- 3 ingdevice has high current gain, low internal feedback, high power gain andlow equivalent base resistance. Its frequency response may beconsiderably improved by operating the device after it has beenelectrically treated with a distance between collector and emitterelectrodes of no more than 5 mils.

What is claimed is:

1. A semi-conductor device comprising a semiconducting body, a baseelectrode, an emitter electrode, a collector electrode, said electrodesbeing in contact with said body, said device being electrically treatedby passing a short and intense pulse of current in the reverse directionbetween said collector and base electrodes under a condition of steadycurrent flow in the reverse direction between said collector and baseelectrodes and in the forward direction between said emitter and baseelectrodes and with said emitter and collector electrodes spaced fromeach other no less than 10 mils, whereby the internal feedback of saiddevice becomes negligible and its current gain is increased.

2. A device as defined in claim 1 wherein said emitter and collectorelectrodes are spaced from each other approximately mils.

3. A semi-conductordevice comprising a semiconducting body, said bodyconsisting of a semiconducting material having a high bulk resistivity,a base electrode, an emitter electrode, a collector electrode, saidelectrodes being in contact with said body, said device beingelectrically treated by passing an electrical charge in the reversedirection between said collector and base electrodes under a conditionof steady current in the reverse direction between said collector andbase electrodes and in the forward direction between said emitter andbase electrodes and with said emitter and collector electrodes spacedfrom each other no less than 10 mils,

whereby the internal feedback of said device becomes negligible and itscurrent gain is increased.

4. A semi-conductor device comprising a semiconducting body, said bodyconsisting of a body having a low bulk resistivity, a base electrode, anemitter electrode, a collector electrode, said electrodes being incontact with said body, said device being electrically treated bypassing an electrical charge in the reverse direction between saidcollector and base electrodes under a condition of steady current flowin the reverse direction between said collector and base electrodes andin the forward direction between said emitter and base electrodes andwith said emitter and collector electrodes spaced from each other noless than 10 mils, whereby the internal feedback of said device becomesnegligible and its current gain is increased. H

5. A semi-conductor device comprising a semiconducting body, said bodyconsisting of a low bulk resistivity material, a base electrode, anemitter electrode, a collector electrode, said electrodes being incontact with said body, said device being electrically treated bypassing an electrical charge in the reverse direction between saidcollector and base electrodes under a condition of steady current flowin the reverse direction between said collector and base electrodes andin the forward direction between said emitter and base electrodes andwith said emitter and collector electrodes spaced from each other noless than 10 mils, said emitter electrode being then moved toward saidcollector electrode so that their spacing is no more than 5 mils,whereby the internal feedback of said device becomes negligible and itscurrent gain is increased.

6. A semi-conductor device comprising a semiconducting body, a baseelectrode, an emitter electrode, a collector electrode, an auxiliaryelectrode, said electrodes being in contact with said body, said bodyconsisting of a semi-conducting material having a low bulk resistivity,said auxiliary electrode being spaced from said collector electrode by adistance of the order of 10 mils or more, said emitter electrode beingspaced from said collector electrode by a distance which is less thanthe first named distance, said device being electrically treated byimpressing an electrical charge in the reverse direction between saidcollector and base electrodes while a steady current is permitted toflow in the reverse direction between said collector and base electrodesand in the forward direction between said auxiliary electrode and saidbase electrode, thereby to provide an equivalent base resistance ofpredetermined relatively low value when measured in electrode by adistance of approximately 15 mils,

said emitter electrode being spaced from said collector electrode by adistance of not more than 5 mils, said device being electrically treatedbyimpressing an electrical charge in the reverse direction between saidcollector and base electrodes while a steady current is permitted toflow in the reverse direction between said collector and base electrodesand in the forward direction between said auxiliary electrode and saidbase accesses 13 electrode, said emitter electrode being. adapted toprovide an amplifieroroscillator withsaidbasecollector electrodes.

8". A semi-conductor device comprising: a semi-- conducting. body; a.base electrode; an; emitter electrode, a collector electrode; anauxiliary electrode, saidi electrodes being in. contact with: saidbody,. said: body consisting; of: a semi-conducting. materialihaving a.low bulk resistivity. said, auxile iary; electrode: being spacedfromsaid collector electrodezby. adistance: of not less thanmils;saidemitter electrode-bein spaced.- from said. G01,-= lect'or'electrode. by a distance of approximately 2 mils,.said devicebeingelectrically treated by mor pressing arr electrical. charge. in: thereverse di.-' motion; between .said. collector and base electrodeswhileza steady current permitted to flow. irrthe reverse directionbetween said. collector and. base electrodes and, in; the forwarddirection between said auxiliary electrode and said base: electrode,thereby to provide anequivalent base: resistance of: the. order of '70.ohms.- or. less when; measured in circuit with said baseelectrode, saidcollector electrode. and said. emitter electrode;

9. A semi-conductor device comprising-,asemiconducting body; a baseelectrode, an emitter electrode, a collector electrode, an auxiliaryelectrode; said.- electrodes being, in contact. with. said body, saidbody consisting of a, semi-conducting material having a:lowbulltresistlvitysaid auxiliary electrode being spaced from saidcollector electrodeby a distanceofapproximately L5.- mils, said: emitterelectrode being, spaced fromsaid. collector electrode by a distanceofapproximately 2 mils,.said device being electrically treated byimpressing an electrical charge in. the reverse direction between saidcollector and base electrodes while a steady current is permitted toflow in the reverse direction between said collector and base electrodesand in the forward direction between said auxiliary electrode and saidbase electrode, thereby to provide an equivalent base resistance of theorder of 70 ohms or less when measured in circuit with said baseelectrode, said collector electrode and said emitter electrode.

10. The method of preparing a semi-conducting device including asemi-conducting body, a base electrode in contact with said body, anemitter and a collector electrode, said method comprising the steps ofpositioning said emitter and collector electrodes in contact with saidbody at a distance of not less than 10 mils from each other, applying asteady electrical current in the reverse direction between saidcollector and base electrodes and in the forward direction between saidemitter and base electrodes, and simultaneously impressing a short andintense pulse of current in the reverse direction between said collectorand base electrodes.

11. The method of preparing a semi-conductor device including asemi-conducting body, a base electrode in contact with said body, anemitter and a collector electrode, said method comprising the steps ofpositioning said emitter and collector electrodes in contact with saidbody at a distance of approximately mils from each other, causing asteady electrical current to flow in the reverse direction between saidcollector and base electrodes and in the forward direction between saidemitter and base electrodes and simultaneously impressing a short andintense pulse oi current in the reverse direction between said collectorand base electrodes.

12. The method or preparing a semi-conductor device including asemi-conducting body of low bull'cresi'sti'vity; a' base: electrode in:contact with. said body, an emitter and a collector: electrode;saidimethod. comprising thesteps of. positioning said emitter: and.collector electrodes in; contactwith said: body at. a, distance at not.less-r than 10 mils from each. other; causing: a. steady: current tnflow' in: the: reverse: direction. between said:. cola lector and base.electrodes. and in. the forward directiombetweenzsaidemitter andbaseielectrodes and SiIIIlllllfll'iBQllSlY impressing an. electricalcharge; in the: reverse direction between: said col.- lector'and base:electrodes. while said emitter electrode spacedthererromby saiddistance, in..- terrupting saidz. current flQWi, and -mo.ving; saidemitter electrode: towards said collector electrode and into contactwithsaid bodyat a distance: or the order; or 5. mils or. less from: saidcollector electrode, for limb operation. of said device; in electricalcircuits.

13.. The method of preparing asemi-conductor device including asemi-conducting body, a. base electrode: in contact with v said. body anemitter electrode, a. collector: electrode and; an. auxiliary,electrode, said method comprising the. steps of. positioning said:auxiliary electrode and said cola lector electrode. in:contactwithsaidhody at-a dis-' tance of not less than 10 mils from eachother; causing a. steady current to fiovv in the. reverse directionbetween said collector and. base. electrades and in theforward directionbetween said auxiliary electrode. and said. base. electrode: andsimultaneously impressing. an. electricalv charge. in the.- reversedirectionbetweensaid: collector and base electrodes and positioningsaidemitter electrode incontactwithsaid body atla distanceirom saidcollector. electrode not more than 5 mils, whereby said device isadapted to be utilized with said base electrode, said collectorelectrode and said emitter electrode.

14. The method of preparing a semi-conductor device including asemi-conducting body of low bulk resistivity, a base electrode incontact with said body, an emitter electrode, a collector electrode andan auxiliary electrode, said method comprising the steps of positioningsaid auxiliary electrode and said collector electrode in contact withsaid body at a distance or" approximately 15 mils from each other,causing a steady current to flow in the reverse direction between saidcollector and base electrodes and in the forward direction between saidauxiliary electrode and said base electrode and simultaneouslyimpressing an electrical charge in the reverse direction between saidcollector and base electrodes, and positioning said emitter electrode incontact with said body at a distance from said collector electrodeoiapproximately 5 mils, whereby said device is adapted to be used inelectrical circuits with said base electrode, said collector electrodeand said emitter electrode.

15. A semiconductor device comprising a. semiconducting body, said bodyconsisting of a semiconducting material having a high bulk resistivityin the range of 10 to 20 ohm-centimeter, a base electrode, an emitterelectrode, a collector electrode, said electrodes being in contact withsaid body, said device being electrically treated by passing anelectrical charge in the reverse direction between said collector andbase electrodes under a condition of steady current in the re-' versedirection between said collector and base electrodes and in the Iorwarddirection between said emitter and base electrodes and with said emitterand collector electrodes spaced from each other no less than 10 mils,whereby the internal 15 feedback of said device becomes negligible andits current gain is increased.

16. A semiconductor device comprising a semiconducting body, said bodyconsisting of a body having a low bulk resistivity in the range of 2 to8 ohm-centimeter, a base electrode, an emitter electrode, a collectorelectrode, said electrodes being in contact with said body, said devicebeing electrically treated by passing an electrical charge in thereverse direction between said collector and base electrodes under acondition of steady current flow in the reverse direction between saidcollector and base electrodes and in the forward direction between saidemitter and base electrodes and with said emitter and collectorelectrodes spaced from each other no less than 10 mils. whereby theinternal feedback of said device becomes negligible and its current gainis increased;

17. A semiconducting device comprising a semiconducting body, said bodyconsisting of a low bulk resistivity material having a resistivity inthe range of 2 to 8 ohm-centimeter, a base electrode, an emitterelectrode, a collector electrode, said electrodes being in contact withsaid body, said device bein in contact with said body, said device beingelectrically treated by passing an electrical charge in the reversedirection between said collector and base electrodes under a conditionof steady current flow in the reverse direction between said collectorand base electrodes and in the forward direction between said emitterand base electrodes and with said emitter and collector electrodesspaced from each other no less than 10 mils, said emitter electrodebeing then moved toward said collector electrode so that their 3 spacingis no more than 5 mils, whereby the inl6 ternal feedback of said devicebecomes negligible and its current gain is increased.

18. A semiconductor device comprising a semiconducting body, a baseelectrode, an emitter electrode, a collector electrode, an auxiliaryelectrode, said electrodes being in contact with said body, said bodyconsisting of a semiconducting material having a low bulk resistivity inthe range of 2 to 8 ohm-centimeter, said auxiliary electrode beingspaced from said collector electrode by a distance of the order of 10mils or more, said emitter electrode being spaced from said collectorelectrode by a distance which is less than the first named distance,said device being electrically treated by impressing an electricalcharge in the reverse direction between said collector and baseelectrodes while a steady current is permitted to flow in the reversedirection between said collector and base electrodes and in the forwarddirection between said auxiliary electrode and said base electrode,thereby to provide an equivalent base resistance of predeterminedrelatively low value when measured in circuit with said base electrode,said collector electrode and said emitter electrode.

' BERNARD N. SLADE.

References Cited in the flle of this patent UNITED STATES PATENTS NumberName Date 2,502,479 Pearson et al Apr. 4, 1950 2,524,033 Bardeen Oct. 3,1950 2,524,035 Bardeen et a1. Oct. 3, 1950 2,563,503 Wallace Aug. 7,1951 2,577,803 Pfann Dec. 11, 1951

